Sheet molding compound having improved surface characteristics

ABSTRACT

A composite part made from a sheet molding compound is disclosed as having improved characteristics over traditional sheet molding compound composite parts. The composite part may be made from a unique sheet molding compound material having a resin impregnated filamentized fiber layer and a resin impregnated fiber layer prior to compaction. The resin impregnated filamentized fiber layer side prevents the movement of partially filamentized or unfilamentized fibers to the visible surface of the composite part when the part is molded. The resin impregnated filamentized fiber layer may be contain a conductive filamentized fiber such that the surface of a sheet molding compound may be conductive and be capable of being electrostatically sprayed.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present invention claims priority from Provisional Application Ser.No. 60/328,860 entitled “Sheet Molding Compound Having ImprovedCharacteristics, filed Oct. 12, 2001, which is incorporated herein byreference.

TECHNICAL FIELD AND INDUSTRIAL APPLICABILITY OF THE INVENTION

The present invention relates generally to reinforced fiber compositesand more specifically to sheet molding compounds having improvedconductive and/or surface characteristics.

BACKGROUND OF THE INVENTION

In the manufacture of fiber reinforced resin products, sheet moldingcompounds are frequently used. Sheet molding compounds offer anappealing solution for the production of Class A surface parts comparedto steel both in terms of cost and coefficients of thermal expansion.

Sheet molding compounds consist of a mixture of a liquid thermosettingresin, particulate filler and chopped reinforcement fibers, such asglass fibers. In most cases, the resin and chopped fibers are sandwichedbetween films of plastic material to form a laminated sheet that iswound in rolled form or festooned for storage. The laminated sheet isstored under conditions that will not result in final curing of theresin, but will allow the paste to thicken to a desired moldingviscosity range, typically between 30,000 and 50,000 centipoise(MilliPascal seconds). At the time of use, the protective carrier filmis removed and the laminated sheet is cut into blanks, or plies, of adesired shape and size. The plies are then molded to form a curedcomposite part. In most applications, multiple plies of the laminatedsheets are used in the composite structure and typically comprisebetween 25 and 50% of the die/tool's surface area. When the laminatedsheets are molded, the resin and glass flow within the mold under heatand pressure to cover the entire surface of the mold. Sheet moldingcompounds are used in a variety of applications that require aestheticappeal, corrosion resistance, lighter weight dimensional control andhigh strength.

One deficiency with currently available sheet molding compounds is thatthe charge typically does not form a Class A type surface parts whencured. This is due to the fact that the chopped fibers move to thesurface of the sheet molding compound to form surface imperfections.Further, the fiber used in some sheet molding compounds typically doesnot flow well in the mold, and this creates surface imperfections suchas surface pores. Thus, sheet molding compounds require sanding andpolishing, or otherwise reworking to be used in applications requiring adesired surface appearance.

Yet another problem with surface characteristics occurs when thesecomposite parts formed from the sheet molding plies are painted. Paintpops may be caused by the release of volatile liquids (such as water,styrene or di-vinyl benzene monomer) from the sheet molding paste or bythe release of moisture or solvents contained within fiber bundlesduring the curing process are quite common, typically affecting 5-10% ormore of painted SMC composite parts. This leads to substantial cost interms of rework and waste.

In addition, to allow a long and uniform flow that will produce awavefree surface, the fibers used in sheet molding compounds aretypically provided by the glass manufacturer as bundles or “splits” ofmultiple filaments. The act of impregnating the bed of chopped fibersbetween two layers of sheet molding compound paste often leaves airtrapped within the composite sheet, most often besides the bundles wheresmall differences in surface tension adversely affects the wetting ofthe bundles or splits. Unfortunately, this bundling may also includeentrapped air which, when released during the flow, produces tinybubbles which travel slowly under a pressure gradient. To evacuate thesebubbles, it is useful to have the molding compound flow to fill out thetool to allow the action of the pressure gradients to move those airbubbles towards the edge of the flow front and thus towards the edge ofthe part. Such large flow typically calls for loading the tool by acharge representing 50% or less of the area of the part

It is therefore highly desirable to improve the surface characteristicsof sheet molding compound. This would allow sheet molding compound partsto be used in a wider variety of composite applications wherein surfacequality is a concern.

SUMMARY OF THE INVENTION

It is thus an object of the present invention to improve the physicaland surface characteristics and electrostatic sprayability of compositesparts made of sheet molding compound composite sheets.

The present invention addresses the above object and comprises acomposite part may be made from a unique sheet molding compoundcomposite sheet having a thin resin surface layer, a resin impregnatedfilamentized fiber layer, a resin impregnated unfilamentized orpartially filamentized fiber layer, and a second resin paste layer. Theresin impregnated filamentized fiber layer side acts as a barrier toprevent the movement of partially filamentized or unfilamentized fibersinto the thin resin surface layer of the composite part when the part iscompacted, molded and cured. This presents a visible surface that isresin rich and porous free, which is shown to improve surfacecharacteristics of the composite part without adversely affectingstrength and stiffness characteristics.

Other objects and advantages of the present invention will becomeapparent upon considering the following detailed description andappended claims, and upon reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a cross-sectional view of a sheet molding compound havingimproved surface characteristics according to one preferred embodimentof the present invention;

FIG. 1B is a cross-sectional view of a prior art sheet molding compound;

FIG. 2A is a schematic diagram for making the sheet molding compound ofFIGS. 1A and 1B;

FIG. 2B is an alternate schematic diagram for making the sheet moldingcompound of FIGS. 1A and 1B;

FIG. 2C is a close-up view of the funnel shaped dispensing device ofFIG. 2B;

FIG. 2D is an enlarged partial cross sectional view of the funnel shapeddispensing device shown in FIG. 2B.

DETAILED DESCRIPTION AND PREFERRED EMBODIMENTS OF THE INVENTION

Referring now to FIG. 1A, a sheet molding compound made in accordancewith a preferred embodiment of the present invention is generally shownas 10 prior to compaction. The sheet molding composite (SMC) sheet 10,from top to bottom, is shown having an upper carrier film layer 12, atop resin paste layer 14, a resin impregnated unfilamentized orpartially filamentized fiber layer 16, a resin impregnated filamentizedfiber layer 18 (including paste 18′ and filamentized fibers 57) and abottom carrier film layer 20. Of course, the order of the layering fromtop to bottom for a finished composite part made from this sheet moldingcompound is reversed, as the resin impregnated filamentized fiber layer18 forms the class A surface side desired when the SMC sheet 10 is madeinto a finished part. The process for forming the SMC sheet 10 of FIG.1A is shown below in FIGS. 2A and 2B. Additionally, the cross-section ofFIG. 1B maybe made using this device, provided the paste 18′ does notinclude filamentized fibers 57, and therefore the shown bottom layer 13of FIG. 1B does not include these fibers as does the layer of paste 18of FIG. 1A (one skilled in the art appreciates that the layer of paste18 (and the paste 18′) in the remaining figures could be replaced by anonfilamentized paste, or layer of nonfilamentized paste 13, whereappropriate).

The compositions of the resin-containing layers 14, 18 used in thepresent invention are variations to formulations currently used formolding Class A surface and/or structural parts. In addition to thepolyester resin (which may include the thermoplastic, thermoset,reactive monomer, etc. as known to one skilled in the art), theformulation contains fillers such as calcium carbonate, a resininhibitor and initiator (catalyst), an alkaline earth oxide or urethanethickening agent, and an internal mold release agent. Of course, otheradditives may be added depending upon the desired characteristics of thepaste and finished composite part.

For the unfilamentized or partially filamentized fiber layer 16formulation, chopped fibers (shown as 58 in FIG. 2A) are also introducedto the formulation. These chopped fibers 58 preferably comprise betweenapproximately 0.25 and 60 percent by weight of the formulation. Anysuitable chopped fiber may be used in the invention. Preferably, thechopped fiber 58 is be selected from fibrous materials that are commonlyknown in the art, such as glass, carbon, natural fibers, polymers andother fiberizable materials known in the art, or mixtures thereof.

For the resin-impregnated filamentized fiber layer 18 formulation,chopped and filamentized or milled fibers are mixed between about 0.25and 30% by weight in the formulation without fillers. Any suitable fiberthat may be filamentized, flaked or milled can be used in the invention.

A preferred composition for the resin paste layer 14 and the resinimpregnated filamentized fiber layer 18 are shown below in Table 1 and2, respectively. As noted herein, the glass fibers shown in table 2 maybe supplemented with, or replaced by, other fibers, such as carbonfibers or flakes, preferably in the range of about 0.1 to 10% by weightof the filamentized paste 18 and replacing a portion of the glass fibercontent. One preferable composition for a conductive resin impregnatedfiber layer 18 is shown in Table 3 below. TABLE 1 SMC RESIN PASTE LAYER14 WEIGHT INGREDIENTS % MANUF. NAME DESCRIPTION T341 16.95 AOC/AlphaOwens Thermosetting Corning Polyester Resin in styrene T154 7.24AOC/Alpha Owens Thermoplastic Corning Polyester resin in styrene Styrene3.13 Ashland Styrene monomer DVB 1.33 Dow Divinyl benzene P710 0.88 BASFPolypropylene oxide PBQ 0.008 Aldrich P-benzoquinone CBA-60 0.88 WitcoNon-ionic surfactant 1300 × 40 0.59 B.F. Goodrich Hycar Rubber instyrene TBPB 0.53 Atofina T-butyl perbenzoate catalyst Cal St 1.18Mallinckrodt Mold Release Agent Huber W-4 62.02 Huber Calcium carbonateRP510 1.83 AOC/Alpha Owens Thermoplastic Corning polyester resin inStyrene Zn St 0.15 Mallinckrodt Mold release agent PDI-1805 0.03 FerroIron pigment Huber W-4 2.66 Huber Calcium carbonate CaO 0.53 C.P. HallAlkaline earth oxide thickener Water 0.05

TABLE 2 FILAMENTIZED LAYER 18 PASTE Function Component Weight percentTable 1 Resin Paste 14 Sheet Molding Resin 72-73%  Formulation (may beless some or all fillers) Owens Corning R25H E-type glass 27-28% reinforcement

TABLE 3 CONDUCTIVE FILAMENTIZED LAYER 18 PASTE Weight Function Componentpercent Table 1 Resin Paste 14 Sheet Molding Resin  72-73% Formulation(may be less some or all fillers) Toray 300 Conductive Carbon Fiber0.1-10% Owens Corning 954 or 973 E-type glass reinforcement 0.1-15%

Referring now to FIG. 2A, one preferable assembly process is shown formaking a compacted SMC sheet 77 from the SMC sheet 10 of FIG. 1A isgenerally shown as 50. The assembly process begins by unrolling thebottom carrier film layer 20 from a roll or reel 52 and transporting itacross a carrier belt 54. Of course, in other embodiments, the carrierbelt 54 is not necessary where the tensile strength of the carrier film20 is sufficiently strong to hold the entire SMC sheet 10. The resinimpregnated filamentized fiber layer 18 is then introduced onto the filmlayer 20 in the form of a wet paste 18′ from a traditional dispensingdevice 17. The device 17 preferably meters the paste 18′ using a doctorblade 56, generally an upside down weir blade. The device illustratedhere is illustrated with an arcuate rear side opposite the doctor blade56, but one skilled in the art appreciates a rectangular doctor box maybe used as well.

Partially filamentized or unfilamentized fiber 58 is then chopped usinga chopper 60 onto the resin impregnated filamentized fiber layer 18. Anupper carrier film layer 12 is unrolled from a roll or reel 62 and asecond resin paste layer 14 is deposited onto the second carrier film 12using another traditional dispensing device 17. The second resin pastelayer 14 is deposited as a wet paste 14′ onto the inner side of theupper carrier film 12. The thickness of the second resin paste layer 14is controlled using a doctor blade 66. The upper carrier film layer 12and second resin paste layer 14 is then rolled around a roller 68 andlaid on top of the chopped glass fiber 58 such that the second resinpaste layer 14 is below the upper carrier film layer 12. This forms theSMC sheet 10 shown in FIG. 1A. A wire mesh belt 70 compacts the SMCsheet 10 to form a compacted SMC sheet 77 of a desired area weight priorto rolling onto a take up roll 72. By controlling the amount of pastes14′ and 18′ deposited by the respective doctor blades 66, 56, by asimple gap adjustment, one skilled in the art can control both theoverall compacted sheet 77 weight and the percentage of filamentizedreinforcement material that is contained within each compacted compositesheet 77.

As the film layer 20 passes under the device 17, the film layer 20 pullsthe bottom of the viscous paste 18′, and may form a puddle of pastewithin the device 17. The viscous paste 18′ may therefore move in acircular pattern, thereby causing a meniscus to form between the backedge of the paste puddle and the film (a void exists between the rearwall of the paste adjacent the film due to a radius formed on the puddleof paste). Depending upon the film speed and the paste viscosity, themeniscus may be as long as a few centimeters. Periodically, possibly dueto film stretching, the meniscus collapses and air is trapped within thepaste 18′. This trapped air exits underneath the doctor blade 56 in theform of bubbles, resulting in a resin film layer having non-uniformthickness, or can form fisheyes in the final surface. This can causelocal regions having higher or lower glass content within the pastefilm, which in turn can cause unwet regions in the molding compound.

In an alternative embodiment, as shown in FIG. 2B, a funnel-shapeddispensing device 17B replaces one or more of the traditional dispensingdevices 17. In one embodiment, both illustrated devices comprise suchfunnel-shaped devices, although not illustrated as such in FIG. 2B. Thefunnel-shaped dispensing device 17B helps to prevent the entrapment ofair that is common in traditional dispensing devices such as device 17,as described in the preceding paragraph. To control viscosity in thedispensing device 17B, heat or cooling may be applied to the device 17Bto maintain a constant temperature, and thereby better enable andcontrol the viscosity and flow therefrom. Heat may be applied to thedevice 17B near the exit 22 of the device 17B to decrease the viscosityof the paste 18′ and thereby improve wet-out of the glass fibers or matwithin the sheet 10. In this regard, the heat source (not shown) couldbe applied against or within a wall 24 of the device 17B near the exit22 or by using the dividing plate 23 as a heat source within thevertical feeding slot 21. Alternatively, a volumetric paste extrusiondevice may be employed.

The output of the device 17B is controlled by controlling the viscosityof the paste 18′ through composition and temperature, plus controllingthe pressure within the feeding slot 21, which may be accomplished bycontrolling the height of the paste in the device 17B, and may includean optional pressurization of the device 17B through known mechanicalmeans (not shown). Accordingly, by controlling the pressure,underfeeding and overfeeding of the doctor blade may be avoided, therebyavoiding too thin, or too thick application (or a mess), respectively.Further, one skilled in the art appreciates that more than one funnelmay be provided in series, and accordingly more than one type of pastemay be deposited onto the sheet; for example, the first funnel mayinclude a non-filamentized paste to provide a resin rich layer on theoutside of the part, and a filamentized paste may be deposited by asecond funnel adjacent the nonfilamentized paste.

As shown in FIG. 2B, the new funnel-shaped dispensing device 17B ispreferably attached to the doctor box, and more preferably the lip of aconventional doctor blade, as shown in FIG. 2A. The height of the paste18′ is controlled via a float valve or similar device so one does notoverfeed the doctor blade 56 and force excessive paste underneath theblade 56. The device 17B contains a foot 19 that extends out into themain dispensing area that ensures that the film layer 20 does not catchwhen the machine is in operation. The foot 19 is adjusted to have asmall gap between it and the film layer 20 that is sufficient to preventthe paste 18′ from flowing out the back of the dispensing device 17B.Further, the dispensing device 17B has a vertical feeding slot 21, whichis preferably divided into two or more narrower slots 21′ by one or moredividing plates 23, each such slot 21, 21′ forming a column of paste.The first such slot 21′ nearest the foot 19 first contacts the carrierfilm 20. In the event that the paste deposited from the first such slot21′ includes air bubbles or incompletely coats the film 20, eachsubsequent slot 21′ will help to coat over any imperfection in the pastefrom the preceding slots 21′. Thus, the multi-slotted funnel-shapeddispensing device 17B is engineered to reduce trapped air or voidswithin the paste 18′, and to form a layer 18 with uniform weight andthickness. Preferably, the width of the slots 21 and 21′ are adjustableby either installing fewer/additional, thinner/thicker plates 23, and/oradjusting walls 24. In a preferred embodiment the foot 19 is positionedbetween about 0.03-0.25 inch above the film 20, and the tip of thedoctor blade 56 is positioned between about 0.05-0.125 inches above thefilm 20, however these gaps will depend upon the paste composition,viscosity, and overall operating conditions.

Each batch of compacted SMC sheet 77 is then allowed to mature andthicken thereby increasing viscosity at approximately thirty-two degreesCelsius for approximately one to fourteen days prior to any moldingapplication. The batch may then be further processed by cutting the SMCsheet 10 to an appropriate ply or laminate size, removing the upper andlower carrier films 12,20, molding the remaining material to anappropriate shape in a heated matched metal or composite die, and curingit under heat and pressure to make a finished composite part (notshown). Preferably, the curing step is done at approximately 5-10 MPA(750-1500 psi) at about 140-163 degrees Celsius (280-325 Degrees F) forabout one-half to three minutes.

During the compaction step described above, excess resin from the resinpaste layer 14 and resin impregnated filamentized fiber layer 18penetrates within and through the partially filamentized orunfilamentized fiber 58 to form the discrete resin impregnatedunfilamentized or partially filamentized fiber layer 16.

However, the filamentized fibers 57 within the resin impregnatedfilamentized fiber layer 18 generally do not significantly penetratewithin this fiber layer 16 during compaction. The compacted SMC sheet77, when cured, forms a composite part in which visible surface layerforms a resin rich and nearly porous free layer that has improvedsurface characteristics with less surface pores as compared withtraditional sheet molding compound composites.

While the above example indicates only one ply of SMC sheet 77, it isunderstood that more than one ply is typically used to form a compositepart. The number of plies of the SMC sheet 77 used to form the compositearticle varies as a function of the thickness (i.e. volume) of thecomposite part desired and the weight per square meter of the SMC sheet77, but typically ranges from two to four plies. In a preferredembodiment, a top ply of the SMC sheet 77 and one or more plies ofconventional SMC, such as those produced in FIG. 11B, made according tothe prior art are placed in the mold. This forms a composite part havinga Class A surface side on a visible side of the composite part, and anon-class A surface that is usually found on the non-visible side. Ifboth the top and bottom surface of the composite part formed need ClassA surfaces, then a top ply and bottom ply of the compacted SMC sheet 77may be used, with one or more plies of sheet molding compound madeaccording to the prior art contained within these sheets 77. In anotherpreferred embodiment, the ply has a sheet weight adequate to form thecomposite part with a single ply.

In addition, if conductive materials such as carbon or nickel coatedcarbon or glass fibers are used in the filamentized fiber layer 1 8, acured composite part having improved electrostatic sprayabilitycharacteristics may be realized. Such conductive fibers may be used inaddition to, or instead of, glass fibers. Similarly conductive flakes,fibrils, powders, or carbon or nickel coated carbon or glass fibers orconductive particles may be used in the resin impregnated filamentizedfiber layer, each of which is to be considered as conductive fibers forthe purposes of this disclosure. Further, by concentrating theconductive materials within the fiber layer 18 at a location which isvery close to the surface of the composite part, less conductivematerial is needed within the composite part as compared withtraditional sheet molding compound composite parts having conductivematerial, which reduces raw material costs.

While the invention has been described in terms of preferredembodiments, it will be understood, of course, that the invention is notlimited thereto since modifications may be made by those skilled in theart, particularly in light of the foregoing teaching.

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 8. A method for making a single ply of a sheetmolding composite sheet comprising the steps of: introducing a firstcarrier film layer; introducing a first resin paste layer onto saidfirst carrier film layer using a paste dispensing device, said firstresin paste layer comprising a resin and a plurality of filamentizedfibers; introducing a layer of chopped filamentized or unfilamentizedfibers onto the top surface of said first resin paste layer; introducinga second resin paste layer onto said layer of chopped or unfilamentizedfibers using a second paste dispensing device; introducing a top carrierfilm layer onto said second resin paste layer to form a sheet moldingcomposite sheet; and compacting said sheet molding composite sheet toform a single ply of sheet molding compound.
 9. The method of claim 8,wherein the step of introducing a first resin paste layer comprises thestep of introducing a first resin paste layer onto said first carrierfilm layer using a paste dispensing device, said first resin paste layercomprising a resin and a plurality of filamentized fibers, wherein saidplurality of filamentized fibers comprise between approximately 0.3 and30% by weight of the formulation of said resin paste without fillers.10. The method of claim 8, wherein the step of introducing a first resinpaste layer comprises the step of introducing a first resin paste layeronto said first carrier film layer using a paste dispensing device, saidfirst resin paste layer comprising a resin and a plurality offilamentized fibers, wherein said plurality of filamentized fiberscomprise between approximately 0.3 and 30% by weight of said pastewithout fillers and is selected from the group consisting offilamentized glass fibers, filamentized carbon fibers, filamentizedconductive fibers, and filamentized natural fibers.
 11. The method ofclaim 8, wherein the step of introducing a first resin paste layercomprises the step of introducing a first resin paste layer onto saidfirst carrier film layer using a paste dispensing device, said firstresin paste layer comprising a resin and a plurality of filamentizedE-type glass fibers, wherein said plurality of filamentized E-type glassfibers comprise between approximately 0.3 and 30% by weight of theformulation of said paste without fillers.
 12. The method of claim 8,wherein the step of introducing a layer of chopped filamentized orunfilamentized fibers onto the top surface of said first resin pastelayer comprises the step of introducing a layer of chopped filamentizedor unfilamentized fibers onto the top surface of said first resin pastelayer, wherein said wherein said layer of filamentized or unfilamentizedfibers comprise between approximately 0.25 and 60% by weight of theformulation of the sheet molding compound.
 13. The method of claim 8,wherein the step of introducing a layer of chopped filamentized orunfilamentized fibers onto the top surface of said first resin pastelayer comprises the step of introducing a layer of chopped filamentizedor unfilamentized fibers onto the top surface of said first resin pastelayer, wherein said wherein said layer of filamentized or unfilamentizedfibers is selected from the group consisting of glass fibers, carbonfibers, and natural fibers.
 14. The method of claim 8, wherein the stepof compacting said sheet molding composite sheet to form a single ply ofsheet molding compound comprises the step of compacting said sheetmolding composite sheet to form a single ply of sheet molding compound,wherein a portion of the resin contained in said first resin paste layerand said second resin paste layer penetrates said unfilamentized orpartially filamentized fibers to form a discrete resin impregnatedunfilamentized or partially filamentized fiber layer.
 15. A method formaking a composite part having improved surface characteristicscomprising: forming a single ply of a sheet molding composite sheet, themethod of forming said single ply comprising the steps of: (a)introducing a first carrier film layer; (b) introducing a first resinpaste layer onto said first carrier film layer using a paste dispensingdevice, said first resin paste layer comprising a resin paste and aplurality of filamentized fibers; (c) introducing a layer of choppedfilamentized or unfilamentized fibers onto the top surface of said firstresin paste layer; (d) introducing a second resin paste layer onto saidlayer of chopped or unfilamentized fibers using a second pastedispensing device; (e) introducing a top carrier film layer onto saidsecond resin paste layer to form a sheet molding composite sheet; (f)compacting said sheet molding composite sheet to form a single ply ofsheet molding compound. thickening said single ply; cutting said singleply into a plurality of moldable plies having a desired shape;introducing at least one of said plurality of moldable plies into amold, wherein said first resin paste layer is closer to a visiblesurface than said second resin paste layer in a top ply of said at leastone of said plurality of moldable plies; and curing said at least one ofsaid plurality of moldable plies at a first pressure and a firsttemperature for a sufficient time to form the composite part.
 16. Themethod of claim 15, wherein the step of curing said at least one of saidplurality of moldable plies comprises the step of curing said at leastone of said plurality of moldable plies at about 140-163 degrees Celsiusand between approximately 5-10 Mpa for between approximately one-halfand three minutes.
 17. The method of claim 15, wherein the step of (b)introducing a first resin paste layer comprises the step of (b)introducing a first resin paste layer onto said first carrier film layerusing a paste dispensing device, said first resin paste layer comprisinga resin and a plurality of filamentized fibers selected from the groupconsisting of a plurality of filamentized E-type glass fibers and aplurality of conductive fibers, wherein said plurality of fiberscomprise between approximately 0.3 and 30% by weight of said pastewithout fillers.
 18. The method of claim 17, wherein the conductivefibers comprise one of filamentized fibers and partially filamentizedfibers.
 19. The method of claim 15, wherein the step of (c) introducinga layer of chopped filamentized or unfilamentized fibers onto the topsurface of said first resin paste layer comprises the step of (c)introducing a layer of chopped filamentized or unfilamentized fibersonto the top surface of said first resin paste layer, wherein saidwherein said layer of filamentized or unfilamentized fibers comprisebetween approximately 0.25 and 60% by weight of the formulation of thesheet molding compound.
 20. The method of claim 15, wherein the step of(c) introducing a layer of chopped filamentized or unfilamentized fibersonto the top surface of said first resin paste layer comprises the stepof (c) introducing a layer of chopped filamentized or unfilamentizedfibers onto the top surface of said first resin paste layer, whereinsaid wherein said layer of filamentized or unfilamentized fibers isselected from the group consisting of glass fibers, carbon fibers, andnatural fibers.
 21. The method of claim 15 further comprising the stepof introducing at least one ply of a traditional sheet molding compositesheet on top of said at least one of said plurality of moldable plieswithin said mold, wherein an outer one of said at least one of saidplurality of moldable plies is located along a visible surface of thecomposite part when molded.
 22. The method of claim 15, wherein the stepof (f) compacting said sheet molding composite sheet to form a singleply of sheet molding compound comprises the step of (f) compacting saidsheet molding composite sheet to form a single ply of sheet moldingcompound, wherein a portion of the resin contained in said first resinpaste layer and said second resin paste layer penetrates saidunfilamentized or partially filamentized fibers to form a resinimpregnated unfilamentized or partially filamentized fiber layer. 23.The method of claim 15, wherein the composite part is made from a singleone of said plurality of moldable plies.
 24. The method of claim 23,wherein the step of (b) introducing a first resin paste layer comprisesthe step of (b) introducing a first resin paste layer onto said firstcarrier film layer using a paste dispensing device, said first resinpaste layer comprising a resin and a plurality of filamentized fibersselected from the group consisting of a plurality of filamentized E-typeglass fibers and a plurality of conductive fibers, wherein saidplurality of fibers comprise between approximately 0.3 and 30% by weightof said paste without fillers.
 25. The method of claim 24, wherein theconductive fibers comprise one of filamentized conductive fibers andpartially filamentized conductive fibers.
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 33. A single ply of a compacted sheet molding composite sheetused for making composite parts having an improved surfacecharacteristics comprising: an upper carrier film layer; a first resinpaste layer; a resin impregnated chopped unfilamentized fiber layer; aresin impregnated filamentized fiber layer; and a bottom carrier filmlayer.
 34. The compacted sheet molding composite sheet of claim 33,wherein the composition of the resin component of said first resin pastelayer and said resin impregnated chopped unfilamentized fiber layer andsaid resin impregnated filamentized fiber layer comprises a polyesterresin.
 35. The sheet molding compound of claim 33, wherein saidcomposition of said first resin paste layer and said resin impregnatedchopped unfilamentized fiber layer and said resin impregnatedfilamentized fiber layer further comprises fillers, a resin inhibitorand initiator, an alkaline earth oxide, and an internal mold releaseagent.
 36. The sheet molding compound of claim 33, wherein the fibercomposition of said resin impregnated filamentized fiber layer comprisesfilamentized E-type glass fibers.
 37. The sheet molding compound ofclaim 33, wherein the fiber composition of said resin impregnatedfilamentized fiber layer further comprises filamentized conductivefibers.
 38. The sheet molding compound of claim 33, wherein the fibercomposition of said resin impregnated filamentized fiber layer furthercomprises conductive fibers.
 39. A single ply of a compacted sheetmolding composite sheet used for making composite parts having animproved surface characteristics comprising: an upper carrier filmlayer; a first resin paste layer; a resin impregnated chopped partiallyfilamentized fiber layer; a resin impregnated filamentized fiber layer;and a bottom carrier film layer.
 40. The compacted sheet moldingcomposite sheet of claim 39, wherein the composition of the resincomponent of said first resin paste layer and said resin impregnatedchopped partially filamentized fiber layer and said resin impregnatedfilamentized fiber layer comprises a polyester resin.
 41. The sheetmolding compound of claim 39, wherein said composition of said firstresin paste layer and said resin impregnated chopped partiallyfilamentized fiber layer and said resin impregnated filamentized fiberlayer further comprises fillers, a resin inhibitor and initiator, analkaline earth oxide, and an internal mold release agent.
 42. The sheetmolding compound of claim 39, wherein the fiber composition of saidresin impregnated filamentized fiber layer comprises filamentized E-typeglass fibers.
 43. The sheet molding compound of claim 39, wherein thefiber composition of said resin impregnated filamentized fiber layerfurther comprises filamentized conductive fibers.
 44. The sheet moldingcompound of claim 39, wherein the fiber composition of said resinimpregnated filamentized fiber layer further comprises conductivefibers.